AWS Lambda functions are executed in containers. When a Lambda is first executed, the appropriate runtime (Node.js, Python etc.) container is started, your code is loaded from S3, the interpreter is initialised and your handler is called. After execution, the container is essentially paused, if another execution of the same function is requested in some undefined amount of time, the same container is resumed and reused for subsequent execution. Otherwise, the container is deleted and any new execution will trigger the above process again. It is most unlikely, however, that specifically Docker containers are used. One of the popular ways to check if a process is running in a Docker container is to check for the existence of the file ./dockerenv or grep for docker in /proc/self/cgroups - this test fails on Lambda. If you want to have a certificate in AWS and Docker then you must take up the following Docker Training Course and AWS Training Course. I am also mentioning a video tutorial for these topics which you must watch to learn all the basics of AWS and Docker.
AWS:
Docker: